The Study Of Effect Of Mineral Admixtures On Concrete Anticorrosive Performance

The durability of concrete has always been the focus of concrete design.With the county's development strategic shift to the western,more and more infrastructure buildings are located in the west,such as the West-East Gas Pipeline Project and the UHV underground concrete project.However,the conditions of China's western salt lake area is complex,due to the chloride ions,sulfate ion corrosion,the service life of the local concrete that has not yet reached the design standard had failed.Therefore,the durability of concrete in salt lake area restricts the sustainable development of western infrastructure.Aimming at the the chloride and sulfate corrosion in the western salt lake area,this paper carried out a series of studies through consulting a large number of literatures.In this paper,three mineral admixtures with fly ash,slag and silica fume were selected as the object of study,and design 16 concrete mix,the rapid chloride ion migration coefficient method(RCM method)and electric flux method were used to establish the relationship between mineral admixtures and the resistance to chloride ion of concrete.;from the aspects of compressive strength,pore structure,microstructure and hydration product structure,the method of dry-wetting cycles sulfates were used to establish the relationship between mineral admixtures and the resistance to sulfate attack of concrete,and finally established a life prediction model of concrete,the research content has the following aspects:(1)Mixing and Optimizating of Concrete.The anticorrosive properties of concrete are mainly achieved by means of mineral admixtures.Therefore,single mixed,double mixed,three mixed were considered,16 kinds of mixing ratios(including the reference mixing ratio that has no admixture)were designed under the conditions of satisfying strength and easiness.The results show that the concrete compressive strength of 16 kinds of mix ratios reaches to C3 5,the slump of fresh concrete is 180?220mm,and the gas content controll at 4%?6%.(2)Study on Mineral Admixtures and Chloride Permeability.In this paper,rapid chloride ion transport coefficient method(RCM method)and electric flux method were used to study the chloride ion resistance of concrete at 28d age.The results show that the chloride ion transport coefficient(RCM)is less than 9×10-12m2/s,the electric flux is less than 1400C of 16 kinds of concrete mix;fly ash and slag can reduce the permeability of concrete obviously.When the admixture is double mixed,the chloride ion resistance of concrete is better than that single mixed,the chloride ion resistance of concrete with three admixture is better than that of double mixed.(3)Study on Mineral Admixture and Concrete Resistance to Sulfate Attack.In this paper,the dry-wettingt cycle tests of 16 kinds of concrete were carried out by using the dry-wetting cycles sulfates method,and compared with the concrete under the standard curing condition,the relationship between admixture and the corrosion resistance of concrete to sulfate was studied from the change in concrete surface,compressive strength and corrosion resistance.The results show that there are significant differences in the appearance of the specimen after 90 times of dry-wetting cycles sulfates.fly ash and slag can improve resistance to sulfate attack.When the admixture is double and three mixed,the concrete resistance to sulfate attack is better than that single mixed.(4)Study on Anticorrosive Mechanism of Concrete.In this paper,the intrinsic mechanism of hydration product structure,pore structure and anticorrosive properties of different anticorrosive concrete was analyzed by means of hydration kinetic model,scanning electron microscopy(SEM)and X-ray(XRD).The results show that under the erosion of sulphate,the porosity and average pore size of various concrete increases with the increase of the number of dry-wetting cycles sulfates,and the pore uniformity gradually decreases.Under the condition of standard,the content of calcium hydroxide was decreased greatly with the increase of the admixture content and the curing age,and the hole of concrete was small and less,the structure was more compact.After 90 days of sulphate circulation,the reference concrete with no admixtures are porous,and contain more ettringite,but the concentration of samples that mix with admixture(single,double,three)is gradually denser,the contents of calcium hydroxide and ettringite are correspondingly reduced.(5)Prediction of concrete life.In this paper,a new concrete structure durability evaluation model was established based on Duracrete model.The results show that the model is reasonable.When with the admixture,the concrete concrete life is higher than that concrete with no admixture.And when with three admixture,concrete has longest life.